HYDROGEOLOGICAL INVESTIGATIONS OF SPRINGS IN BELL COUNTY, TEXAS, NEAR THE STILLHOUSE HOLLOW RESERVOIR

This research area consists primarily of complex karst geology and supports numerous springs that played a key role in providing fresh drinking water for early inhabitants of the region. Situated 63 miles north of Austin, TX, Bell County is home to the expanding communities Killeen, Belton, Fort Cavazos, and Temple, which are experiencing exponential growth due to the I-35 corridor development. The study focuses on the springs downstream of the Stillhouse Hollow Reservoir Dam. The two study sites are Chalk Ridge Falls Spillway Creek and Tahuaya Scout Camp. Spillway Creek has four springs that emerge from the Edwards Limestone with Spring A flowing most consistently and Spring B being the second most consistent. Springs C and D flow primarily during periods of high recharge. The Tahuaya Spring is a moderately large spring that was donated to the Boy Scouts of America in 1932 and was originally known as Camp Spicewood Springs. It has deep ties to frontier heritage and later settlements that utilized the spring flow to power a gristmill. These springs are being investigated to provide a more comprehensive understanding of hydrogeology utilizing innovative research approaches. Through compiling information from the Texas Water Development Board Groundwater Database, such as well reports and water quality analyses, along with field measurements, isotopic data (¹⁸O and ²H), and geochemical analyses for common ions we examine the springs’ flow rates, ionic composition, and isotopic signatures. The discharge from Tahuaya is monitored by a pressure transducer, which continuously record temperature, conductivity, and water level at five-minute intervals which can be correlated to reservoir levels and rainfall events recorded on the USGS station at the Stillhouse Hollow Dam. Additionally, periodic manual discharge measurements with a Swoffer water velocity meter were conducted to establish a rating curve for the pressure transducer at Tahuaya Spring. Finally, we assessed the presence of Zebra Mussel eDNA at Tahuaya Spring to evaluate the extent of influence the reservoirs have on groundwater in the surrounding areas. Overall, the findings of the study will help provide a better understanding of the local groundwater systems and how they may interact with the reservoirs of Bell County. The results will be used to inform local water management strategies and support conservation efforts.